The present invention generally relates to skull flap fastening systems. More particularly, the present invention relates to a surgical tool which facilitates the tensioning of a cranial-flap clamp used in such fastening systems.
When brain surgery is performed, it is often necessary to remove a piece of the skull to provide access to the brain. This surgical procedure is often referred to as a craniotomy. A portion of the cranial vault is removed or folded back in a flap to permit surgical access to the cranial contents, such as the brain. This is often done with a hand-held, gas-powered surgical tool similar to a small router. After a small hole is made in which the bit of the router is placed, the bit is then guided to cut out the piece of the skull required. The blade cuts a small gap so that the piece removed does not fit back into its hole exactly.
After the brain operation, the skull flap must be replaced and held in position until the skull heals. Previously, a series of matching small holes were drilled in the edge of the skull and the edge of the skull flap. Sutures were then passed through the corresponding holes and the flap secured back into the skull opening from which it was taken. However, due to the inexact fit caused by the router bit, the flap sat slightly below the surface of the skull, resulting in a depressed area visible through the skin.
Stainless steel wire was substituted for the suture material, which is stronger than the suture material, but more cumbersome. The wire was prone to failure, particularly if over-twisted, and was found to be palpated through a skin scalp if not properly buried. Also, the introduction of computed tomography (CT), demonstrated extensive metal artifacts caused by these wires. Further, the common problem of skull flap settling remained.
More recently, cranial mini-plate fixation systems were developed. While these systems have been successful, they are time consuming and very expensive.
Even more recently, alternative cranial fixation systems comprised of cranial-flap clamps having opposing closure members, often disks, in which one disk is fixed to an end of a stem, while the other is movable along the stem towards the opposing closure member to clamp the skull and bone flap together. This method is faster than any of the other methods and less expensive and time consuming than the mini-plate fixation systems.
Tools have been devised for gripping the pin or stem of the clamp, and then pressing together the disks into a clamping formation. However, the process often takes more than one tool to complete, thus requiring both hands of the surgeon. Some of the tools require calibration before use. Another disadvantage of such tools is that they require special cleaning processes due to their complicated design. Some surgeons have also found these tools somewhat complicated in use and not intuitive.
Accordingly, there is a need for a surgical tool which is intuitive and easy to use. During tensioning of the clamp, the tool should not require calibration. The tool should also be able to perform the clamping procedure alone, so that a hand of the surgeon is free from the procedure. The tool should not require special cleaning processes, nor disassembly before its next use. The present invention fulfills these needs and provides other related advantages.
The present invention resides in a surgical tool for tensioning a cranial-flap clamp having opposing closure members variably positioned relative to each other on a stem for refixing a bone flap to the cranium. The tool generally comprises first and second handles which are pivotally attached to one another intermediate their first and second ends. A first jaw extends from the first end of a first handle, and has an aperture which is configured to accept the stem therethrough. A second jaw extends from the first end of the second handle, and has an aperture configured to accept the stem therethrough. A ratcheting mechanism is associated with the second jaw which selectively locks the stem in place within the second jaw aperture. Typically, the first and second jaw apertures comprise open-faced channels extending the width of the first and second jaws.
The ratcheting mechanism preferably comprises a pawl pivotally attached to the second jaw and having teeth on an outer edge thereof. A spring is associated with the jaw and the pawl to bias the pawl in a locking position. The ratcheting mechanism is typically positioned within a cavity of the second jaw which is at least partially contiguous with the second jaw aperture. A portion of the pawl extends without the second jaw when the pawl is in its biased position. The first jaw is configured to contact the pawl and position the pawl in an unlocked position when the jaws are brought towards one another.
The tool includes means for biasing the first and second jaws into contact with one another, such as a spring positioned between the first and second handles. Typically, the spring comprises first and second leaf springs. A first end of the first leaf spring is attached to the second end of the first handle. A first end of the second leaf spring is attached to the second end of the second handle. The second ends of the first and second leaf springs are connected to each other so as to bias the jaws into contact with one another.
In use, the cranial-flap clamp is properly positioned between the cranium and the bone flap. The stem is inserted through the aperture of the first and second jaws. As the tool is actuated by squeezing the second end of the handles, the pawl of the ratcheting mechanism locks the stem in place within the second jaw aperture, while the first jaw presses against the sliding closure member so as to bring the closure members towards one another in a clamping formation. Once proper tension is achieved, the stem is trimmed from the clamp.
The surgical tool of the present invention is advantageous over prior existing tools in that it is easy and convenient to use. Moreover, the tool does not need to be calibrated before use, and does not require disassembly nor special cleaning procedures after use.
Other features and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.